You can download the update by selecting Software Update from the General menu on your iOS device.

● LTE support for more carriers (complete list of supported carriers at www.apple.com/iphone/LTE/)● Purchase movie tickets through Fandango with Siri (USA only)● iTunes Match subscribers can now download individual songs from iCloud● New button to reset the Advertising Identifier

NEW FEATURE NOT DISCUSSED BEFORE:
In the music app, while connected to the same network, you can play your Mac iTunes music and turn on the screen saver as well as using airplay on the Apple TV.
Pretty friggin cool.

There's one more new thing! Siri now works with Spanish, and probably other languages too (previously, spanish could be selected as a language in Siri preferences but it was only available for Dictation).